1. Field of the Invention
The present invention relates to a light source and an optical coherence tomography apparatus using the light source.
2. Description of the Related Art
Superluminescent diodes (may alternatively abbreviated as SLD hereafter) are a semiconductor light source that emits light having a wide range of a spectral distribution similarly to light emitting diodes while permitting a comparatively high optical power of equal to or more than 1 mW to be obtained similarly to semiconductor lasers. Due to their characteristics, SLDs receive attention in the medical and measuring fields where high-resolution is required, and are used as the light source of, for example, optical coherence tomography (OCT) apparatus, with which tomographic images of body tissue can be obtained.
In order to obtain a high-resolution tomographic image, a light source that emits light having a light emission spectrum of a wide full with at half maximum can be used. Examples of structures used in such a light source include: an asymmetric dual quantum well structure having different quantum well widths described in IEEE Photonics Technology Letters, vol. 8, no. 11, pp. 1456-1458, 1996; a plurality of quantum well structures with varied compositions; and an active layer having a single quantum well structure. With these structures, it is intended that light emission spectra from different energy levels are superposed with one another so as to obtain a wide full width at half maximum.